{"id":1317,"date":"2016-07-28T01:38:46","date_gmt":"2016-07-28T01:38:46","guid":{"rendered":"http:\/\/blogs.lincoln.ac.nz\/gis\/?p=1317"},"modified":"2023-05-07T04:04:43","modified_gmt":"2023-05-07T04:04:43","slug":"getting-to-the-points","status":"publish","type":"post","link":"https:\/\/blogs.lincoln.ac.nz\/gis\/getting-to-the-points\/","title":{"rendered":"Getting to the Point(s)"},"content":{"rendered":"

In this post we look at how points can be mapped from their raw coordinates in a text file or table.<\/em><\/p>\n

So the GIS Helpdesk<\/a> got a call last week – a postgrad was having some trouble mapping some points.\u00a0 Ah, it reminds me of that time all those years ago, before I knew about GIS, when, after doing some GPS surveying I simply wanted to see all those points on a map so I could tell if they were in the right place.\u00a0 I saw how easy it was and, for better or worse, I was hooked.<\/p>\n

And that’s a familiar scenario – you’ve got some x and y coordinates recorded somewhere and want to translate them to a map.\u00a0 It’s not a difficult task, once you know how.\u00a0 So in this case, the student wanted to map the locations of meteorological stations in the Waipara catchment.\u00a0 Amongst his 25 data files of rainfall, humidity and solar radiation, he had one that looked like this:<\/p>\n

\"StationFile\"<\/a><\/p>\n

This is mapping gold and gives us all we need to get the points on a map.\u00a0 Starting with the first line, we’ve got details about the station data; an ID number, name, latitude, longitude and elevation.\u00a0 Then a line for each station with commas separating each item.\u00a0 For mapping purposes it’s the latitude and longitude that we’re most interested in.\u00a0 The negative in front of the latitude is pretty unambiguous – we are either north or south of the equator.\u00a0 There’s a bit of ambiguity in the longitude as we could be either east or west, but the absence of a negative sign will be taken as east of the prime meridian<\/a> at Greenwich.\u00a0 Importantly, these are in decimal degrees rather than degrees minutes and seconds, which makes things a tad bit easier.\u00a0 So a quick inspection shows us that we’ve got the data we need to map these eight points.<\/p>\n

Next, we’ll add this text file straight into ArcGIS – I’ll use Pro <\/a>here and just add the text file straight onto a new map:<\/p>\n

\"ProAddData\"<\/a><\/p>\n

We could just have easily added an Excel sheet or a dbf table.\u00a0 Once on the map I can open the table with a right-click.\u00a0 Because it uses commas to separate values, it’s easily read in:<\/p>\n

\"TextTable\"<\/a><\/p>\n

To map those points, all I need to do is right-click on the table name and go to “Display X Y Data”<\/p>\n

\"DisplayXY\"<\/a><\/p>\n

This will open up a new tool in a pane at the right where I can set some parameters about which field is my x coordinate and which my y.\u00a0 It’s “smart” enough to recognise Long and Lat appropriately:<\/p>\n

\"DisplayXYTool\"<\/a><\/p>\n

It’s also recognised that the data’s coordinate system is WGS84<\/a> (the lat\/long system used with GPS).\u00a0 Clicking “Run at the bottom of the tool should deliver up some points on the map:<\/p>\n

\"PointsOnMap\"<\/a><\/p>\n

Et voila!\u00a0 I’ve also added the Waipara catchment boundary to the map to give it some context.\u00a0 If I’m happy enough with this for mapping purposes, I could next create a layout.\u00a0 If I were thinking of using these points for some analysis, my next step would likely be to convert the layer’s coordinate system from lat\/long to New Zealand Transverse Mercator, as the rest of my data would likely be in that system.<\/p>\n

So mapping points is quite easy as long as you’ve got the right information (the coordinates).\u00a0 And that’s the whole point.<\/p>\n

C<\/p>\n","protected":false},"excerpt":{"rendered":"

In this post we look at how points can be mapped from their raw coordinates in a text file or table. So the GIS Helpdesk got a call last week – a postgrad was having some trouble mapping some points.\u00a0 Ah, it reminds me of that time all those years ago, before I knew about […]<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-1317","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/blogs.lincoln.ac.nz\/gis\/wp-json\/wp\/v2\/posts\/1317","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.lincoln.ac.nz\/gis\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.lincoln.ac.nz\/gis\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.lincoln.ac.nz\/gis\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.lincoln.ac.nz\/gis\/wp-json\/wp\/v2\/comments?post=1317"}],"version-history":[{"count":1,"href":"https:\/\/blogs.lincoln.ac.nz\/gis\/wp-json\/wp\/v2\/posts\/1317\/revisions"}],"predecessor-version":[{"id":4146,"href":"https:\/\/blogs.lincoln.ac.nz\/gis\/wp-json\/wp\/v2\/posts\/1317\/revisions\/4146"}],"wp:attachment":[{"href":"https:\/\/blogs.lincoln.ac.nz\/gis\/wp-json\/wp\/v2\/media?parent=1317"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.lincoln.ac.nz\/gis\/wp-json\/wp\/v2\/categories?post=1317"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.lincoln.ac.nz\/gis\/wp-json\/wp\/v2\/tags?post=1317"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}